topic 8 Flashcards
Anabolic
Builds complex molecules, Are endergonic, biosynthetic, Ex.Photosynthesis
Catabolic reaction
Break down complex molecules, Are exergonic, degradative, Ex. Cellular Respiration.
The type of reaction that breaks down complex organic molecules with the release of energy is called catabolism
Exergonic
Reactions that occur when the products of a chemical reaction have less energy than the reaction’s reactants or substrates. They tend to occur in degradative reactions- complex molecules broken into simpler materials.
Endergonic
Reactions that occur when the products of a chemical reaction have more energy than the reactants or substrates of the reaction. They occur in biosynthetic reactions- complex molecules are produced.
Redox reactions
oxidation & reduction
Oxidation
Loss of electrons, Gain of Oxygen, loss of hydrogen, Results in many C-O bonds and a compound with a lower potential energy
Reduction
Gain of electrons, Loss of oxygen, Gain of hydrogen, results in many C-H bonds, results in a compound with a higher potential energy
Enzyme
substrate specifically is made possible by enzyme structures. Enzymes are very complex protein molecules with high molecular weights. The higher levels of protein structure allows for enzymes to form unique areas, such as the active site.
The induced fit model
The conformational changes and induced fit are the result of changes in the R-groups (globular- tertiary level of organization) of the amino acids at the active site of the enzyme, as the enzyme interacts with the substrate or substrates.
Mechanism of Enzyme Action
The surface of the substrate contacts the active site of the enzyme.
The enzyme changes shape to accommodate the substrate.
A temporary complex called the enzyme-substrate complex forms.
The activation energy is lowered and the substrate is altered by the rearrangement of the existing atoms.
The transformed substrate, the product, is released from the active site.
The unchanged enzyme is then free to combine with other substrate molecules.
Competitive Inhibition
In competitive inhibition, a molecule called a competitive inhibitor competes directly with the usual substrate of the active site of an enzyme. The result is that the substrate will have fewer encounters with the active site and rate of chemical reaction will be decreased. The competitive inhibitor must have a structure similar to the substrate to function in this way.
Competitive Inhibition may be reversible or irreversible. Reversible competitive inhibition may be overcome by increasing the substrate concentration- there are more substrate molecules to bind with the active sites as they become available and chemical reaction may occur more rapidly
Noncompetitive Inhibition
Involves an inhibitor that does not compete for the enzyme’s active site. In this case, the inhibitor interacts with another site on the enzyme.
It is also referred to as allosteric inhibition and the site the inhibitor binds to is called the allosteric site.
Feedback/End-product Inhibition
End-product inhibition prevents the cell from wasting chemical resources and energy by making more of a substance than it needs. Many metabolic reactions occur in an assembly-line type of process so a specific end product can be achieved.
Each step of the assembly line is catalyzed by a specific enzyme. When the end product is present in a sufficient quantity, the assembly line is shut down- this is usually done by inhibiting the action of the enzyme in the first step of the pathway.
As the existing end product is used by the cell, the first enzyme is reactivated. The enzyme that is inhibited and reactivated is an allosteric enzyme. When present in higher concentrations, the end product binds with the allosteric site of the first enzyme- bringing about inhibition.
Lower concentrations of the end product result in fewer bindings with the allosteric site of the first enzyme, and therefore, activation of the enzyme.
Anaerobic Respiration
If no oxygen is available, the pyruvate enters into anaerobic respiration. This occurs in the cytoplasm and it does not result in ATP. The products of anaerobic respiration are lactate or ethanol and carbon dioxide.
Aerobic Respiration
If oxygen is available, the pyruvate enters aerobic respiration in the mitochondria of the cell. This process results in the production of a large number of ATPs, carbon, and water.
Oxidation vs. Reduction reactions (redox) in CR
C6H12O6+6O2→ 6H2O+6CO2+energy
Glucose is oxidized because electrons are transferred from it to oxygen. The protons follow the electrons to produce water. The oxygen atoms that occur in the oxyzgen molecules on the reactant side of the equation are reduced. There is a large drop in the potential energy on the product side of the equation.
In the krebs cycle for cellular respiration
Any time there is a 5 to 4, carbon was removed in the krebs cycle
Anytime Co2 is released
Redox- NADH and FADH2 are produced. NAD+ and FAD+ picked up electrons
Phosphorylation
ADP becoming ATP
Glycolysis
Glycolysis is the process of sugar splitting. It uses no oxygen and occurs in the cytosol of the cell. No organelles are required. The sugar splitting proceeds efficiently in aerobic and anaerobic environments. Glycolysis occurs in both prokaryotic and eukaryotic cells.
Two ATPs are used to start the process.
A total of four ATPs are produced: a net gain of two ATPs.
Two molecules of NADH are produced.
The pathway involves substrate-level phosphorylation, lysis, oxidation, and ATP formation.
The pathway occurs in the cytoplasm of the cell.
The pathway is controlled by enzymes. Whenever ATP levels in the cell are high, feedback inhibition will block the first enzyme of the pathway, slowing down the process
Link Reaction
Once glycolysis has occurred and there is oxygen present, pyruvate enters the matrix of the mitochondria via active transport. Inside, pyruvate is decarboxylated, a reaction involving the loss of a carbon in the form of carbon dioxide to form the 2-carbon acetyl group. This is the link reaction. The removed carbon is released as carbon dioxide, a waste gas. The acetyl group is then oxidized with the formation of reduced NAD+. Finally, the acetyl group combines with coenzyme A (CoA) to form acetyl CoA.
The link reaction is controlled by a system of enzymes and produces acetyl CoA.
Krebs Cycle
a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate—derived from carbohydrates, fats, and proteins —into carbon dioxide. Acetyl CoA enters the Krebs cycle from the link reaction to continue the aerobic respiration. (0 ATP are used, 2 ATP are produced.)
ETC
Most of the ATPs from glucose catabolism are produced. This is the first stage of cellular respiration where oxygen is actually needed and occurs within the mitochondrial cristae. Embedded in the membranes, involved are molecules that are easily reduced and oxidized. These carriers of electrons (energy) are close together and pass the electrons from one another. One carrier protein is called coenzyme Q/ In this chain, electrons pass from one carrier to another because the receiving molecule has a higher electronegativity and therefore, a stronger attraction for electrons. In the process of ETC, small amounts of energy are released. The sources of the electrons that move down the electron transport chain are coenzymes NADH and FADH2. (O ATP are used, 32 are produced)
Glycolysis products and reactants
Glucose is the reactant, NADH, ATP, ad pyruvic acid are products
Oxidative Phosphorylation products and reactants
NADH and FADH2 are reactants, NADH, FADH2, oxygen, ADP, Pi phosphate are the products
Link reaction products and reactants
Pyruvic acid is a reactant, Acetyl-CoA and NADH are products.
Krebs Cycle
acetyl CoA and oxaloacetate are reactants, and NADH, FADH2, and ATP are products
The Role of fermentation pathways in CR
Fermentation pathways allow glucose to be continuously broken down to make ATP due to the recycling of NADH to NAD+.
Electron flow through the process of CR
electrons from glucose move gradually through the electron transport chain towards oxygen, passing to lower and lower energy states and releasing energy at each step. The goal of cellular respiration is to capture this energy in the form of ATP.
Importance of the mitochondrial matrix and cristae in aerobic respiration
The Mitochondrial Matrix: An internal cytosol-like area that contains the enzymes for the link reaction and the krebs cycle.
Cristae: Tubular regions surrounded by membranes that increase the surface area for oxidative phosphorylation and provide a barrier, allowing proton accumulation on one side.
Importance of NADH and FADH2 for the ETC
The sources of electrons that move down the electron transport chain are the coenzymes NADH and FADH2.
Role of oxygen (final electron acceptor) in CR
Oxygen is the final electron acceptor because it has a very high electronegativity and, therefore, a strong attraction for electrons. When the electrons combine with the oxygen, so do two hydrogen ions from the aqueous surroundings. The result is water.
Oxidative phosphorylation (ETC & Chemiosmosis)
Electrons are transferred from NADH and FADH2, through a series of electron carriers, to O2. The electron carriers are proteins embedded in the inner mitochondrial membrane.
Transfer of electrons by these carriers generates a proton (H+) gradient across the inner mitochondrial membrane.
When H+ spontaneously diffuses back across the inner mitochondrial membrane, ATP is synthesized. The large positive free energy of ATP synthesis is overcome by the even larger negative free energy associated with proton flow down the concentration gradient.
The ETC is the first stage of cellular respiration where oxygen is actually needed, and it occurs within the mitochondria. Embedded in the membranes involved are molecules that are easily reduced and oxidized. These carriers of electrons are close together and pass the electrons from one to another because of an energy gradient. Each carrier molecule has a slightly different electronegativity, meaning a different attraction. Most of the carrier proteins are in haem groups.
FADH2 enters the ETC at a lower free energy level than NADH, thus FADH2 allows the production of two ATPs while NADH allows the production of 3 ATPs.
At the very end of the chain, the de-energized electrons combine with available oxygen
Process of chemiosmosis (ATP production)- importance of H+ ions and ATP synthase
Involves an electron transport chain embedded in the membranes of the cristae
Energy is released when electrons are exchanged from one carrier to another
Released energy is used to pump hydrogen ions actively into the intermembrane space
Hydrogen ions come from the matrix
Hydrogen ions diffuse back into the matrix through the channels of ATP synthase
Atp synthase catalyzes the phosphorylation of adp to form ATP
H ions are important because they form a gradient that ATP synthases uses for the production of ATP.
Because of the hydrophobic region of the membrane, the hydrogen ions can only pass through the ATP synthase channel. Some poisons that affect metabolism act by establishing alternative pathways through the membrane, thus preventing ATP production.
Oxidation vs. Reduction reactions
The reduction of carbon dioxide into sugars and oxidation of water into molecular oxygen is involved in photosynthesis.
The light-dependent reaction
occurs in the thylakoids or grana of the chloroplast. A stack of thylakoids make up a granum. Light supplies the energy for this reaction to occur. The ultimate source of light is the sun.
The energy lost from the electrons moving down the electron transport chain drives chemiosmosis (similar to that in respiration) to bring about phosphorylation of ADP to produce ATP.
A photon of light is absorbed by a pigment in Photosystem I. This energy is transferred through several accessory pigments until received by a chlorophyll a (P700) molecule. This results in an electron with a higher energy state being transferred to the primary electron acceptor. The de-energized electron from Photosystem II fills the void left by the newly energized electron.
The electron with the higher energy state is then passed down a second electron transport chain that involves the carrier ferredoxin.
The enzyme NADP reductase catalyzes the transfer of the electron from ferredoxin to the energy carrier NADP+. Two electrons are required to reduce NADP+ fully to NADPH.
NADPH and ATP are the final products of the light-dependent reaction. They supply chemical energy for the light-independent reaction to occur.
Light independent reaction
This occurs within the stroma. The ATP and NADPH produced by the dependent reaction provide the energy and reducing power for the light- independent reaction. Its product is glucose. It involves the calvin cycle.
Uses ATP and NADPH to form triose phosphate
Returns ADP inorganic phosphate and NADP to the light-dependent reaction
Involves the calvin cycle.
Importance of water in the light-dependent reaction
Water is split by an enzyme to produce electrons, hydrogen ions, and an oxygen atom
Cyclic vs. noncyclic flow of electrons
Cyclic: The cyclic photophosphorylation proceeds only when light is not a limiting factor and when there is an accumulation of NADPH in the chloroplast. In this process, light-energized electrons from Photosystem I flow back to the cytochrome complex of the electron transport chain between Photosystem II and Photosystem I. From the cytochrome complex, the electrons move down the remaining electron transport chain allowing ATP production via chemiosmosis.
non-cyclic photophosphorylation- Standard light dependent reaction.
Importance of photosystems II (P680) and I (P700)
Each absorbs light most efficiently at a different wavelength. Photosystem I is most efficient at 700 nanometers (nm) and is labeled as P700. Photosystem II is most efficient at 680 nm and is labelled as P680. These two photosystems work together to bring about a non-cyclical electron transfer. They energize electrons and continue the movements.
Role of pigments & photons in photosynthesis
To absorb light, plants have special molecules called pigments. The major groups are chlorophylls and the carotenoids, which are located in the thylakoids. The regions of organization are called photosystems.
Light energy behaves as if it exists in discrete packets called photons. Shorter wavelengths of light have greater energy within their photons than longer wavelengths. Photons can transfer their energy upon interaction with other particles, which is used in photosynthesis
3 phases of the Calvin Cycle
Carbon fixation: A CO2 molecule combines with a five-carbon acceptor molecule, (RuBP). This makes a sex-carbon compound that splits into two molecules of a three-carbon compount, 3-PGA. This reaction is catalyzed by the enzyme Rubisco.
Reduction: ATP and NADPH are used to convert the 3-PGA molecules into molecules of a three-carbon sugar, G3P. This stage gets its name because NADPH donates electrons to, or reduces, a three-carbon intermediate to make G3P.
Regeneration: Some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Regeneration requires ATP and involves a complex network of reactions.
In order to regain RuBP molecules from TP, the cycle uses ATP.
Process of chemiosmosis
Involves an electron transport chain embedded in the membranes of the thylakoids
2.)Energy is released when electrons are exchanged from one carrier to another
3.)Released energy is used to pump hydrogen ions actively into the thylakoid space
4.)Hydrogen ions come from the stroma
5.)Hydrogen ions diffuse back into the stroma through the channels of ATP synthase
6.)ATP synthase catalyzes the photophosphorylation of ADP to form ATP
H+ ions release energy when they are diffused for the production of ATP
Relationship between CR and Photosynthesis
Photosynthesis converts carbon dioxide and water into oxygen and glucose. Cellular respiration converts oxygen and glucose into water and carbon dioxide. Water and carbon dioxide are by- products and ATP is energy that is transformed from the process.
